To determine the activation energy (Ea) for the reverse reaction from the given graph, we can use the following energy relationship: ∆H=(Ea)‌forward ‌‌‌−(Ea)‌backward ‌ From the graph, we have: ∆H=90‌KJ (Ea)‌forward ‌=215‌KJ Plugging these values into the equation, we get: 90=215−(Ea)‌backward ‌ Solving for (Ea)‌backward ‌ : (Ea)‌backward ‌=215−90=125‌KJ Therefore, the activation energy for the reverse reaction is 125 KJ .